1. Field of the Invention
The disclosed embodiments of the present invention relate to overdriving control and a related circuit, and more particularly, to an overdriving control method with image compression control and a circuit thereof.
2. Description of the Prior Art
In order to save bandwidth usage of an image transmission interface, a liquid crystal display driver IC (such as a thin film transistor liquid crystal display or TFT LCD) will have a built-in memory, such as a static random access memory body (SRAM). The memory is used to temporarily hold image data which has been sent to the driver IC but has not yet been outputted. With developments in display size, resolution, frame rate and color depth, the memory built inside the driver IC needs to increase in capacity in order to cope with the increasing amount of image data transmission. The bandwidth requirements also increase proportionally. In practical applications, image compression technology is utilized to reduce the bandwidth occupied by the memory without significantly degrading display quality.
Liquid crystal molecules in an LCD display have a relatively slow response. It often takes hundreds of milliseconds to go from one value to another and back again so that the molecules can change their direction. The response time of the liquid crystal molecules needs to be less than several milliseconds (e.g. 17 ms) for avoiding perceived motion blur, hence overdrive technology is applied for providing an overshoot voltage to motivate and accelerate the liquid crystal molecules to approach a predetermined position; the voltage will then drop back to an appropriate value (the response time of liquid crystal molecules is proportional to the supply voltage). The overdrive technology is applied in conjunction with the information of the pixel content so that one liquid crystal molecule does not need to change its voltage level or direction if the color of the corresponding pixel remains unchanged; if the color of the corresponding pixel changes, the liquid crystal molecule only needs to move from the present value to the new value corresponding to the changed pixel.
Employing image compression for reducing bandwidth occupied by memory access may degrade the original high-definition quality of the display. Moreover, overdrive further carves up the memory bandwidth, as the more complicated the overdriving process, the more memory and memory bandwidth required. Due to the above-mentioned trade-off between memory bandwidth and quality, there is an urgent need for an innovative overdrive control method which can control image compression processing and overdrive processing.